php - PDOException Error 1064

I've been staring at this code for ever and I can figure out why
it's not working.

$dbh = dbCon();
            // CONNECT TO DATABASE THROUGH FUNCTION 

$sth =
            $dbh->prepare("SELECT * FROM ? WHERE ? = ?");
            
$sth->execute(array($var1, $var2, $var3));
            
$sth->fetch(PDO::FETCH_OBJ);

When
I replace the second line
with:

$sth =
            $dbh->prepare("SELECT * FROM clientDetails WHERE clientID =
            1");

Everything
works fine but when I set var1, 2, 3 to them it doesn't want to work and throws the
following error:

Fatal error:Uncaught exception 'PDOException' with message
'SQLSTATE[42000]:
Syntax error or access violation: 1064 You have an error in
your SQL
syntax; check the manual that corresponds to your MySQL server
version
for the right syntax to use near ''clientDetails' WHERE 'clientID'
=
'1'' at line 1' in /home/cms/functions/functions.php:142 Stack
trace:
0 /home/cms/functions/functions.php(142):
PDOStatement->execute(Array) #1
/home/cms/functions/functions.php(470):
returnData() #2 {main} thrown

in /home/cms/functions/functions.php
on line 142

class="post-text" itemprop="text">

class="normal">Answer

$sth = $dbh->prepare("SELECT
            * FROM " + $var1 + " WHERE " + $var2 + " =
            ?");
$sth->execute(array($var3));